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HomeTech Articles > Replacing 356 Axle Boots

Pelican Technical Article:

Replacing 356 Axle Boots

Difficulty Level 2

Difficulty scale:
Adding air to your tires is level one
Rebuilding a 911 Motor is level ten

Figure 1:
Cracked Axle Boot Leaking Transmission Gear Oil

Figure 2:
Cutting Boot Off After Removing Clamps

Figure 3:
Axle Exposed

Figure 4:
Completed Installation of New Axle Boot

    If your 356 is leaking transmission fluid, then it may very well be old and worn out axle boots.  The axle boots cover the joint that connects the axle to the transmission, similar to the CV joint boots in other cars.   The main difference is that the transmission case is open to the joint, thereby providing it with lubrication from the transmission.  The assembly of the rear axle is shown in our 356 Parts Diagrams Section. As a result, cracked or worn axle boots can leak large amounts of transmission fluid, especially while driving.  In fact, the level of the transmission fluid is normally below the level of the axle boots, so that they usually will not leak when parked.  Only during driving does the gear oil from the transmission get sloshed around in the joint area.  Immediately after driving, the boots may leak what fluid remains inside of them.

     The replacement of the boots is generally a straightforward task.  The first step is to determine if they need replacing at all.  Figure 1 clearly shows an axle boot that is cracked and failing.  Replacement of this boot is necessary, otherwise all of the transmission fluid will eventually leak out.  Check the seams around where the clamps seal the boot.  If there is any doubt, then they should be replaced.  Axle boots are generally pretty cheap (approximately $20 for the pair).  Here's a more detailed list of what you will need:

  • Two Axle Boots
  • About a gallon of Transmission Gear Oil
  • Gear oil pump for filling the transmission

     In order to replace and install the boots, the axles need to be supported evenly, as if the car were sitting on the ground.  This makes the job ideal for using drive-up ramps which support the weight of the car, and keep the axles even.  Be careful when driving on the ramps, or you might overshoot them, like I recently did (photo).  As an alternative to the ramps, you can jack up the car and place it on jack stands, and then place the floor jack under each wheel to support it.  Make sure the parking brake is engaged to lock the wheel.

     You don't need to drain the transmission fluid to replace the boot. However, since you are working on the transmission, and will probably need to top off the fluid later on, it is recommended that you change the transmission oil.  You empty the fluid by removing the cap (Part #13 in the Transmission Exploded View) on the bottom of the transmission near where it mounts to the engine.

     To remove the boot, simply unscrew the inner and outer clamps, and cut the old one off. Cutting the boot with a razor blade is much simpler than removing each and every screw.  The boot with the beginnings of a cut is shown in Figure 2. Simply finish cutting the rubber, and the boot should slip off.  The axle joint without the boot is shown in Figure 3.  Preassemble the screws and washers into the boot before you place it around the axle.  Place the boot on the axle and tighten down the screws with a screwdriver and a nut driver.  The screws do not need to be 'kung-fu death grip' tight.  Just moderately tight, as any huge amount of torque on the screws will deform the boot and most likely make it leak or fail prematurely.

     After the screws are tightened, then start the clamps around each end.  Before you tighten the clamps down, make sure that the seam of the boot is horizontal to the ground.  Figure 4 shows this orientation.  For reference, this photo was taken underneath the car, looking up while lying on my back.  Again, the clamps should be tight, but don't overtighten them as they might strip.

     After the boot is installed, be sure to refill your transmission with fluid, or at least top it off.  If the transmission has been leaking for quite some time, chances are it will be pretty dry inside.  You fill the transmission by removing the filler plug and filling until the level is even with the plug. (Part #12 in the Transmission Exploded View)

   If you have any questions about the procedure in this article, feel free to drop us a line or give us a call.

Comments and Suggestions:
sszakats Comments: In the article for replacing axle boots on a 356, you reference 2 part numbers 19 and 20 from the exploded view diagram. I beleive the part numbers are incorrect. Can you confirm the correct ones for me? Thanks
June 2, 2009
  Followup from the Pelican Staff: - Eugene at Pelican Parts

Thanks for brining this to our attention. The article has now been corrected. The drain plug is #999-064-020-02 (ref #13) and the fill plug is #999-064-019-02 (ref #12).

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